Process for cleaning wastewater and recirculating water in paper production, de-inking and bleaching of pulp

Abstract

Wastewaters and circulation waters in papermaking, in deinking and in pulp bleaching are treated by adsorption of water-soluble anionic compounds and compounds dispersed in water from the wastewaters and circulation waters over finely divided adsorbents which consist of insoluble, only slightly swellable polymers which contain polymerized vinylamine units, and these polymers are used as adsorbents for treating water circulations in papermaking and for treating paper machine wastewaters and wastewaters from the deinking process and from pulp bleaching.

We claim:  
     
       1. A process for treating waste waters and circulation waters in papermaking, in deinking and in pulp bleaching, comprising retaining insoluble impurities and absorbing water-soluble anionic compounds and compounds comprising phenolic resins and monobasic acids and anions thereof dispersed in water from the wastewaters and circulation waters over a finely divided absorbent, wherein the finely divided absorbent is an insoluble, only slightly swellable polymer which is prepared by copolymerizing 
       (a) N-vinylcarboxamides of the formula                    
       wherein R and R 1  are each H or C 1 -C 6 -alkyl, and  
       (c) from 0.1 to 10% by weight, based on the monomer (a) of a compound containing at least two ethylenically unsaturated double bonds as a crosslinking agent, in the absence of oxygen and polymerization initiators to produce popcorn polymers, and eliminating the groups                    
       from at least 0.1% of the polymerized N-vinylcarboxamides of the formula I with the formation of vinylamine units of the formula                    
       wherein R 1  is H or C 1 -C 6 -alkyl.  
     
     
       2. A process as claimed in claim  1 , wherein the absorbents are insoluble, only slightly swellable polymers which are obtainable by copolymerizing monomer mixtures comprising 
       (a) from 24.5 to 95% by weight of N-vinylformamide,  
       (b) from 4.5 to 75% by weight of N-vinylpyrrolidone and  
       (c) from 0.5 to 5% by weight of divinylethyleneurea,  
       the sum of the monomers (a), (b) und (c) always being 100% by weight, to produce popcorn polymers, and subsequently eliminating formyl groups from at least 1% of the polymerized N-vinylformamide units with formation of vinylamine units. 
     
     
       3. The process as claimed in claim  1 , wherein circulation water from a paper machine passes through a layer consisting of a finely divided adsorbent. 
     
     
       4. The process as claimed in claim  1 , wherein wastewater from a paper machine passes through a layer consisting of a finely divided adsorbent. 
     
     
       5. The process as claimed in claim  1 , wherein wastewater from a deinking process passes through a layer consisting of a finely divided adsorbent. 
     
     
       6. The process as claimed in claim  1 , wherein wastewater obtained from pulp bleaching passes through a layer consisting of a finely divided adsorbent. 
     
     
       7. The process as claimed in claim  1 , which comprises fluidizing the finely divided adsorbent in the wastewater or in the circulation water of a paper machine or in the wastewater from the deinking process or from pulp bleaching and separating these fluids from the finely divided adsorbent in each case. 
     
     
       8. A process for treating waste waters and circulation waters in papermaking, in deinking and in pulp bleaching, comprising retaining insoluble impurities and absorbing water-soluble anionic compounds and compounds comprising phenolic resins and monobasic acids and anions thereof dispersed in water from the waste waters and circulation waters over a finely divided absorbent, wherein the finely divided absorbent is an insoluble, only slightly swellable polymer which is prepared by copolymerizing 
       (a) N-vinylcarboxamides of the formula                    
       wherein R and R 1  are each H or C 1 -C 6 -alkyl,  
       (b) other monoethylenically unsaturated monomers copolymerizable with said N-vinylcarboxamides, and  
       (c) from 0.1 to 10% by weight, based on the monomers (a) and (b), of a compound containing at least two ethylenically unsaturated double bonds as a crosslinking agent, in the absence of oxygen and polymerization initiators to produce popcorn polymers, and eliminating the groups                    
       from at least 0.1% of the polymerized N-vinylcarboxamides of the formula I with the formation of vinylamine units of the formula                    
       wherein R 1  is H or C 1 -C 6 -alkyl.